N-Methylformamide (NMF) and its congener, N,N-dimethylformamide (DMF) are polar solvents that are active against experimental human solid tumors in vivo. The aim of this work is to achieve an understanding of the basis of the antineoplastic action of NMF and DMF. This is of particular importance as 1) NMF is currently undergoing clinical trials and 2) these compounds have the unusual ability to suppress the malignant phenotype (e.g. decreased clonigenicity and tumorigenicity) of human colon carcinoma cells. This laboratory has recently obtained evidence that NMF and DMF inhibit the in vitro growth of human colon cancer cells by depleting their intracellular glutathione pools. This is based primarily on the observation that the glutathione precursor, 1-cysteine, restores both growth and the glutathione content of NMF and DMF-treated cells. L-Cysteine also restores the polar solvent-mediated inhibition of the expression of certain cellular oncogenes in these cells. The specific aims of this proposal are: first, to elucidate the precise mechanism by which polar solvents cause a depletion of glutathione and second, to understand how a polar solvent-mediated loss of glutathione can result in growth inhibition. Under this specific aim it will be examined whether glutathione depletion cause membrane alterations, e.g. increased lipid peroxidation, resulting in a decreased ability of these cells' membrane-bound growth factor receptors to respond to endogenous (autocrine-related) or exogenous growth factors, leading to a decreased expression of particular oncogenes. Other hypotheses will be tested. Another specific aim is to examine the exploitability of the above-mentioned findings in the chemotherapy of colon carcinoma, including a) can glutathione repletion therapy using cysteine precursors reverse NMF-induced hepatotoxicity, b) can one take advantage of defects in cysteine metabolism that occur in certain colon tumors and selectively rescue normal tissues from the glutathione-depleting effects of these polar solvents, and c) can these polar solvents be used in combination with other antineoplastic agents, e.g., cis-platin, whose action may be compromised by high intracellular levels of glutathione. The proposed studies on polar solvent action will not only provide information on the basic control mechanisms of colonic cell proliferation and perhaps differentiation, but also insights into better ways of utilizing these agents in the treatment of colon carcinoma.